Add cluster service contracts for AzerothCore realm coordination

[VG-prog]

Summary

This PR lays the shared contract foundation for clustered AzerothCore support in ToCloud9.

The intent is to make the rest of the cluster work explicit at service boundaries instead of relying on ad hoc fields or implicit GUID conventions. It extends the protobuf contracts, generated Go bindings, shared event payloads, GUID helpers, identity helpers, and configuration surface that the gateway, registry, groupserver, guildserver, matchmakingserver, worldserver bridge, and sidecar use to speak the same language.

What changed

• Extended service protobuf contracts for characters, chat, group, guild, matchmaking, registry, and worldserver flows.
• Regenerated the corresponding Go bindings.
• Added shared event payloads and producers/consumers for cluster routing.
• Added shared helpers for account identity, group-state tracing, player GUID conventions, arena team IDs, and WoW power types.
• Added the config knobs needed by clustered services and sidecar clients.

Why this matters

The later runtime changes depend on consistent identity and message shapes. This PR keeps those contracts visible and reviewable before service behavior is layered on top.

Validation

• git diff --check origin/master..HEAD
• env GOCACHE=/tmp/tc9-go-build GOFLAGS=-buildvcs=false go build ./...
• env GOCACHE=/tmp/tc9-go-build GOFLAGS=-buildvcs=false make install

[VG-prog]

Closing this draft because it was opened from a stacked branch while targeting master, so the GitHub diff includes earlier slices and is not an isolated review target.

Replacement: #37 (#37)

That replacement PR presents the current integration honestly as one review surface. Sorry for the review noise.